TEST 2: Bypassing The Radiator Fan Motor Switch
So far, you have confirmed two important things:
One: That the radiator fan motor DOES NOT turn on when your Honda Civic is overheating.
Two: That the radiator fan motor DOES run when you apply battery power and chassis ground directly to its connector (TEST 1).
In this test we're going to jumper together the radiator fan switch connector terminals. This will in effect bypass the radiator fan switch and indirectly test the fan switch.
NOTE: The radiator fan switch is located on your Civic's engine thermostat housing. The thermostat housing is where the lower radiator hose connects to. Photo 2 of 2 in the image viewer will help you to locate it in the engine compartment.
PRECAUTION: This is a very simple test but it does require one very important safety precaution and that is that your Honda Civic must be completely cold (to avoid getting burned).
OK, this is what you need to do:
Disconnect the radiator fan switch from its pigtail connector.
Remember: Your Honda's engine should be cold.
Jumper the pigtail connector's 2 terminals.
IMPORTANT: Use the smallest diameter wire to jumper these two circuits. If you use anything thicker (gauge-wise) you could permanently damage the female metal terminals.
Turn the ignition switch to the On position, but don't start the engine (this test is done with the Key On Engine Off -KOEO).
The radiator fan motor should activate, as soon as you turn the key to the On position (KOEO).
CASE 1: The radiator fan motor came on. This is the normal and expected test result.
This test result tells you several important things:
- The radiator fan motor relay is good (otherwise the fan would not have come on).
- The radiator fan motor and fan motor relay fuses are NOT blown (otherwise the fan would not have come on).
- The wires between the fan switch and radiator fan motor relay are not shorted (otherwise the fan would not have come on).
- The wires between the radiator fan motor and radiator fan motor relay are not shorted (otherwise the fan would not have come on).
Therefore, you can correctly deduce that the fan motor switch is bad and needs to be replaced.
CASE 2: The radiator fan motor DID NOT come on. Recheck your jumper wire connections and retest.
If the fan motor does not come on, then you have eliminated two important components as bad:
- The radiator fan motor.
- The radiator fan motor switch.
What's the next step? Your next step should be to bypass the radiator fan relay and bench-test it. For the ‘how to’ on this, see this tutorial: Radiator Fan Relay Test (2001-2005 1.7L Honda Civic).
Jumper Wire With Alligator Clips With Rubber Insulating Protectors
A very important safety precaution, when applying battery power and ground to the radiator fan motor is to use jumper wires with alligator clips on both ends that have rubber insulating protectors.
These rubber insulated alligator clips are not expensive and taking the time to buy them and use them will help you avoid shorting the jumper wire against some bare metal surface on your Honda Civic.
Where can you buy these alligator clips with rubber insulating protectors? You can buys them at your local Radio Shack.
Where To Buy The Radiator Fan Motor And Save
You can buy just about anything you need for your Honda at your local auto parts store but if you're like me and need to save some bucks... the best offers are online.
Below, in the boxes, are links to the radiator fan motor, the radiator fan switch, and the radiator, which you can check out and compare.
In case you're wondering if these parts fit your specific Honda, once you click on the links and reach the website, they'll ask you for the specifics of your Honda and either confirm that they fit or will help you find the right parts.
More Honda Civic Test Tutorials
You can find a complete list of Honda Civic tutorials in this index: Honda 1.7L Index of Articles.
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Crank Sensor (2001-2005 1.7L Honda Civic).
- Maintenance Required Light Reset (2001-05 1.7L Honda Civic).
- How To Do A Cylinder Balance Test (2001-2005 1.7L Honda).
- How To Test Trouble Code P0141 (2001-2005 Honda 1.7L).
- How To Test The TP Sensor (2001-2005 Honda 1.7L).
- How To Test Trouble Code P0135 (2001-2003 Honda 1.7L).